One possible discovery could offer proof that Tyrannosaurus rex was a scavenger -- evidence of healed-over tyrannosaur bites in other fossils. Most fossilized dinosaurs died from events unrelated to being eaten, so it should be easy to tell whether they survived past attacks from predators. Unfortunately, there are few fossils that show clear evidence of past T. rex bites.
John W. Happ of Shenandoah University suggests a Triceratops whose skull was discovered in 1997 lived for years after being bitten by a T. rex [source: Perkins]. An Edmontosaurus fossil shows evidence of vertebral spines that re-grew after a bite that may have been inflicted by a tyrannosaur [source: Carpenter]. But there are few such examples, and the cause of the bone damage is difficult to prove conclusively. There's also the question of whether any animal would survive long enough for its T. rex bite to heal.
Some of the same evidence used to suggest that T. rex may have been a predator can be interpreted differently. For example, T. rex had tiny arms, especially compared to the prehistoric raptors. But some researchers point out that armlike forelimbs aren't a prerequisite for being a predator -- snakes, for instance, manage without them. One study also defies the idea that these limbs were useless. Kenneth Carpenter of the Denver Museum of Natural History suggests that based on the size, shape and position of the arm bones and shoulder blades, these apparently puny limbs were powerful.
Then there's the matter of the abundance of broken dinosaur teeth some interpret as evidence of eating abandoned bones. If T. rex was a predator, it might have used one of many methods to attack prey, and each could have resulted in broken teeth. Tyrannosaurs might have:
- Ripped through the neck or throat, causing teeth to meet vertebrae and the skull
- Charged at prey with its mouth wide open to inflict a devastating wound, breaking teeth on whatever bones it hit
- Attacked with a bite to the abdomen, hitting ribs in the process
Plus, an animal as large as T. rex may have needed bones for nourishment regardless of whether it killed an animal or found a corpse.
This counterargument even gets down to the defense mechanisms of T. rex's potential prey. Was the neck frill on a Triceratops for protection or sexual display? And did it use its horn for defense against predators or combat with intruders on its territory? Since we have no way to observe the behavior of these animals, we don't really know. The most logical answer may be that Tyrannosaurus rex, like many large predators, was an opportunist, catching fresh meat when possible and eating carrion when necessary.
To learn more about unsolved mysteries of the dinosaur world, see the links below.
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More Great Links
- Abler, William L. "The Teeth of the Tyrannosaurs." Scientific American. Vol. 281, Issue 3. September 1999.
- Alexander, R. McNeill. "Dinosaur Biomechanics." Proceedings of the Royal Society of Biological Sciences. Vol. 273, no. 1596. August 2006. (7/8/2008) http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1634776
- Burress, Charles. "Rattling Bones: Paleontologists Debate T. rex's Nature as a Predator or Scavenger." SFGate. 2/5/2001 (7/8/2008)
- Carpenter, Kenneth and Matt Smith. "Forelimb Osteology and Biomechanics of Tyrannosaurus Rex." Mesozoic Vertebrate Life. Tanke, Darren H. and Kenneth Carpenter, eds. (7/8/2008) http://books.google.com/books?hl=en&lr=&id=mgc6CS4EUPsC&oi=fnd&pg =PA90&dq=tyrannosaurus+predator&ots=370vbK9E-x&sig= vhs3qYGCYm2e51smcZeTE_Xd2PI
- Carpenter, Kenneth. "Evidence of Predatory Behavior by Carnivorous Dinosaurs." Gaia. December 1998.
- Carpenter, Kenneth. "Forelimb Biomechanics of Nonavian Theropod Dinosaurs in Predation." Concepts of Functional, Engineering and Constructional Morphology. Vol. 82, no. 1 2002 (7/8/2008) https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/ theropod%20forelimb.pdf
- Earth. "Tyrannosaurus Droppings." Vol. 4 Issue 6. December 1995.
- Erikson, Gregory M. "Breathing Life into Tyrannosaurus Rex." Scientific American. March 2004 Special Edition.
- Farlow, James O. and Thomas R. Holtz. "The Fossil Record of Predation in Dinosaurs." Paleontological Society Papers. Vol. 8, 2002.
- Fitzgerald, Richard. "How Fast Could Tyrannosaurus rex Run?" Physics Today. April 2002.
- Hecht, Jeff. "The Bigger they Are, the Harder they Fall." New Scientist. 10/7/2995 (7/8/2008) http://www.newscientist.com/article/mg14819982.600-the-bigger-they- come-the-harder-they-fall.html
- Hutchinson, John R. and Mariano Garcia. "Tyrannosaurus Was Not a Fast Runner." Nature. Vol. 415. 2/28/2002
- Leutwyler, Kristen. "Jurassic Jawbreakers." Scientific American. November 1996.
- Lingham-Soliar, Theagarten. "Guess Who's Coming to Dinner: A Portrait of Tyrannosaurus rex as a Predator." Geology Today. January-February 1998.
- Meers, Mason B. "Maximum Bite Force and Prey Size of Tyrannosaurus rex and Their Relationships to the Inference of Feeding Behavior." Historical Biology. Vol. 16, No. 1 March 2002.
- Nicholls, Henry. "T. rex's Shock-absorbing Skull." ScienceNow. 6/9/2004.
- Perkins, Sid. "Healed Scars Tag T. rex as Predator." Science News. Vol. 64, Issue 18, 1/1/2003.
- Ruxton, Graeme D. and David C. Houston."Could Tyrannosaurus rex Have Been a Scavenger Rather Than a Predator? An Energetics Approach." Proceedings of the Royal Society of London B. Vol. 270, 2003.
- Stokstad, Erik. "T. rex Was No Runner, Muscle Study Shows." Science. Vol. 295, Issue 5560, 3/1/2002.
- Tanke, Darren H. "Head-biting Behavior in Theropod Dinosaurs: Paleopathological Evidence." Gaia. No. 15. December 1998.
- UCMP Berkley. "The Tyrannosauridae." (7/8/2008) http://www.ucmp.berkeley.edu/diapsids/saurischia/tyrannosauridae.html